U.S. Pat. No. Re. 29,487 describes a roll-down type earplug comprising a slow recovery viscoelastic polymeric foam and having a size and shape adapted to be compressed, inserted into the human ear canal, and therein allowed to expand to result in an acoustic obturation of the ear canal. Such earplugs have features of easy insertability, comfort, excellent attenuation properties and their ability to be produced in a single size while competently fitting almost the entire adult population. Such an earplug is utilized by first rolling it down between thumb and fingers to the extent that it is compressed in cross section to below the size of the ear canal into which it is to be inserted. The earplug is then inserted into the ear canal and held at the inserted depth with a fingertip for enough time as to allow the polymeric foam to recover sufficiently to seat the plug within the ear canal.
One of the important features of foam compositions for such earplugs is the slow recovery time. In the case of polyvinyl chloride-based earplugs, ADMEX 523®, a polymeric phthalate based plasticizer, has typically been employed to provide the desired slow recovery properties. This plasticizer, however, contains high amounts of monomeric phthalates which may be undesirable for some applications. While these foam compositions are suitable for their intended use, there nonetheless remains a need for earplugs comprising slow recovery foam compositions.